In this fanfiction, for the relationship between Natsu and other characters, Natsu's new Alph Dragon Slayer powers could attract the attention of villains. This would make his friends more protective of him. For instance, Wendy could use her healing magic to help Natsu when he gets injured during battles against enemies interested in his powers. Natsu could also form new friendships with characters who are also interested in the secrets of the Alph Dragon Slayer magic. They could exchange knowledge and experiences, which would in turn develop Natsu's character and his relationships with others.
One plot idea could be that Natsu discovers a new, hidden power within his Alph Dragon Slayer abilities. Maybe he can communicate with ancient dragons that were previously unknown. Another idea is that he has to compete in a tournament against other dragon slayers with unique powers. This would lead to intense battles and character development.
Their relationship can be developed by having them share more personal stories about their past with the dragons. For example, Natsu could tell Wendy about Igneel's funny habits, and Wendy could share her memories of Grandeeney. This would strengthen their bond as siblings who share a common dragon - slayer heritage.
In the fanfiction, their relationship can be developed through mutual growth. Natsu could help Cana become more confident in her magic abilities, and Cana could teach Natsu some wisdom about life. As they see each other improve, they start to respect and admire each other more. This admiration can turn into love over time. For instance, Natsu could be there for Cana when she fails at a big magic spell, and his encouragement could be the turning point in their relationship.
They can develop their relationship by having small, everyday moments. For example, sharing breakfast together as a family, where they talk about their plans for the day. Natsu could show his love for Lucy by being more protective of her and their family in dangerous situations. Also, they could have inside jokes that only their family understands, which would strengthen their bond.
One of the main characters could be Happy, Natsu's loyal flying cat companion. Happy would likely be by Natsu's side during his retirement, still providing his comical relief and support. Another character could be Lucy. She might be concerned about Natsu's retirement decision and try to understand his reasons, or she could also be retiring from her own magical adventures and join Natsu in his new peaceful life.
They could have more deep conversations about their future as a family. For example, discussing how they want to raise their children, what kind of values they want to instill. Also, showing them supporting each other in small daily things, like Lucy helping Natsu with his reading skills and Natsu helping Lucy when she has a tough day at the guild. This would strengthen their bond on a more personal level.
Their relationship could develop through shared battles. When they fight side by side against common enemies, they start to trust each other. For instance, in a fight against a group of dark mages, Natsu and the female demon realize that they complement each other's fighting styles. Natsu's brute force combined with the female demon's more strategic and stealthy attacks make them a powerful duo.
In the 'king of dragon slayer fanfiction', Natsu is likely a central figure. He might have special powers related to slaying dragons, like breathing fire or having enhanced strength. His character could be developed in ways that are different from the original series, perhaps with new relationships and challenges within the fanfiction world.
In some fanfictions, there might be original characters created by the author. For instance, a mysterious figure who has some connection to Natsu's multi - dragon slayer abilities. This character could be an antagonist, testing Natsu's skills, or a mentor, guiding him to master his powers better.
Obviously, Natsu is one of the main characters. He is the strongest dragon slayer in this fanfiction. His friends from Fairy Tail like Lucy, Gray, and Erza are also likely to be main characters. They often support Natsu in his battles and adventures.